Building Electrical Copper Wires THW/THW-2 conductor is suitable for most current wiring solutions for residential, commercial and industrial environments. It is used in service entrance, feeders and branch circuits for permanent installations. THW conductors in sizes 14 AWG to 1000 Kcmil (MCM) can be installed in conduits and other raceways. The temperature of installation shall not exceed 75°C (THW), not exceed 90°C (THW-2).